Purge unit for refrigeration machine



Filed Dec.

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United States Patent 3,410,106 PURGE UNIT FOR REFRIGERATION MACHINE Thomas H. Brockie, Detroit, Mich., assignor to American Standard Inc., a corporation of Delaware Filed Dec. 7, 1966, Ser. No. 599,816 2 Claims. (Cl. 62-195) ABSTRACT OF THE DISCLOSURE This invention proposes a single purge unit for removing foreign non-condensibles and foreign condensib es from a refrigeration machine which uses volatile refrigerant. Features of the purge unit are single shell construction, minimum number of leak-prone joints, easy dis assembly for maintenance, and ability to perform without a purge compressor.

In the drawings:

FIG. 1 is a diagrammatic illustration of a refrigeration machine having a purge unit of the present invention associated therewith.

FIG. 2 is an enlarged sectional view taken through the purge unit used in the FIG. 1 machine.

FIG. 3 is a fragmentary sectional view taken on line 3-3 in FIG. 2.

GENERAL ARRA NGEMENT In FIG. 1 there is shown a conventional refrigeration machine of, for example, fifty tons or more capacity, comprising a tube-shell refrigerant condenser 10, tubeshell refrigerant evaporator 12, and centrifugal refrigerant compressor 14. Condenser is provided with the conventional float chamber 16 which supplies liquid refrigerant to the main liquid line 18 going to evaporator 12. Evaporated refrigerant is discharged from the evaporator to a vapor line 20 going to the inlet of compressor 14. Compressed refrigerant vapor is delivered to a hot gas line 22 leading to condenser 10. Condenser 10 preferably operates somewhat above atmospheric pressure, while evaporator 12 operates at sub-atmospheric pressures.

The illustrated machine is provided with a purge unit 24 designed to rid the treated refrigerant of foreign nortcondensibles such as air carbon dioxide or nitrogen, and foreign condensibles such as water. Unit 24 comprises an upright cylindrical shell which is supplied with impure or or untreated refrigerant gas through a small conduit coming from the upper portion of condenser shell 10. Coolant for separating the non-condensibles may be supplied through a small liquid refrigerant line 32 coming from the liquid supply chamber 16; liquid flow through line 32 is set by a fixed orifice 34. The spent liquid coolant may be discharged from purge unit 24 back to the machine via a liquid line 36 discharging into the low side of the machine, as for example the upper portion of evaporator 12.

The treated condensed refrigerant (freed of the noncondensibles) falls into the lower portion of the purge unit where the foreign condensibles (water) are separated by density differences. The purified refrigerant may be discharged from the purge unit through a liquid line 38 connecting with the evaporator 12 or some point in the system below purge unit pressure. Separated foreign condensibles may be periodically discharged through a manual valve 98.

PURGE SHELL CONSTRUCTION As shown in FIG. 2, the purge unit comprises an upper cylindrical shell section 40 having a flat top wall 42 welded thereto at its upper edge and a flat annular flange plate 44 welded about its lower edge; positioned flatwise against 3,410,106 Patented Nov. 12, 1968 "ice flange 44 is a bottom plate 46, suitable bolts 48 extending through the flange and plate to removably secure the plate on the lower portion of the shell. An O-ring seal 50 may be provided to seal the shell-plate joint. Although the purge unit can be sized within a range of different dimensions, depending on the size of the refrigeration machine, an illustrative shell might have a height of about thirteen inches and a diameter of eight inches, making it quite small in comparison with the refrigeration machine, which might be on the order of fifteen feet in length.

The aforementioned gas line 30 connects with a small cup-like fitting 52 having a hole registering with the orifice 54 in shell 40, whereby a controlled quantity of vapor flows into the space 56 due to the pressure drop existing between condenser 10 and the space 56 within shell 26. The condenser pressure is somewhat above atmospheric pressure, and the pressure in space 56 may be at slightly greater or slightly less than atmospheric pressure. depending on the accumulation of noncondensibles therein.

Removably arranged within shell 26 is an upstanding annular partition 58 of cylindrical tubular configuration, said partition having at least one opening 60 nearits mid point for equalizing the pressure across the partition side wall. The upper edge of partition 58 is welded to a flat circular plate-like roof 62 having a short angle iron spacer element 64 secured thereto for spacing the partition roof assembly from the shell tube wall 42. The lower edge of annular partition 58 is provided with one or more openings 66 which permit liquid to flow from annular chamber 56 inwardly into the space 68 circumscribed by the lower portion of wall 58.

FOREIGN NON-CONDENSIBLE PURGING The gas admitted through fitting S2 is arranged to be cooled by a heat exchange coil 70 located in the annular chamber 56, i.e. in the space between partition 58 and shell wall 40. Heat exchange coil '70 comprises a generally vertical liquid coolant supply conduit 72 brazed onto a pipe 74 which is welded to plate 46. The upper end of conduit 72 connects with a helical conduit 76 which spirals upwardly around the outer surface of partition 58 to a generally U-shaped return bend 78. The return bend connects with a downwardly spiraling helical conduit 80 which has its lowermost convolution connected to a vertical discharge conduit 82, said conduit 82 being brazed onto a pipe (not shown) which is welded to plate 46 in a manner similar to pipe 74. Pipe 74 connects with the aforementioned conduit 32 (FIG. 1). and the corresponding pipe for conduit 82 connects with line 36 (FIG. 1).

Liquid coolant fiows from the high side of the float chamber 16 through conduit 32, pipe 74, conduit 72, upwardly spiraling helical conduit 76, return bend 78, downwardly spiraling conduit 80, vertical conduit 82, and line 36 back to the machine. Helical conduits 76 and 80 may be formed with fins on their outer surfaces to increase condensing surface and improve the cooling action on the gas in chamber 56. The cooling action causes the refrigerant (with foreign eondensibles) to be condensed and to flow gravitationally downwardly to collect in the lower annular chamber designated by numeral 60. The non-condensibles (such as air which has leaked into the system) collect in the upper portion of chamber 56 and move around the peripheral edge of roof 62 into the space 84 between roof 62 and shell top wall 42.

A conventional pressure switch 86 (FIG. 1) connects with space 84 via a pipe 88, and a conventional solenoid valve 90 connects with space 84 via a pipe 92. The solenoid portion of the valve is electrically connected with the pressure switch 86 so that when the pressure in space 84 indicates an accumulation of non-condensible gas and is slightly above atmospheric pressure the solenoid is energized to open the valve and discharge the non-condensibles to the atmosphere.

FOREIGN CONDENSIBLES PURGING Welded to the shell bottom wall 46 is a stand pipe 94 having its open upper end on the same level as the upper edge 96 of the annular tubular partition 98. The stand pipe 94 connects with a manual valve 98 (FIG. 1) which is normally closed. Therefore after a period of service during which foreign condensibles have accumulated in the system a column of liquid will normally collect in stand pipe 94 as well as in the annular chamber 60. Light foreign condensibles, principally water, collect as an upper layer 100 on the main body of relatively pure refrigerant shown as a lower liquid layer 102; the liquid interface is designated by numeral 105. The relatively pure refrigerant will of course have a few parts per million water dissolved therein, and the term pure is therefore used in a comparative sense. Due to the density differences no water will get down to the openings 66 in partition 58. The liquid column in chamber 68 will therefore be pure liquid refrigerant. The lighter water layer will have a surface level 104 somewhat higher than the surface level 106 of the relatively pure refrigerant in annular chamber 68 because the water column has a lesser weight per unit height than the corresponding refrigerant column in chamber 68. The difference in surface level (104 compared to 106) will increase as the amount of liquid impurity increases. Thus the level interface 105 will tend to lower and the surface level 104 will tend to raise as the amount of foreign con densibles increases. At periodic intervals (depending upon the degree of contamination) the manual valve 98 will be opened to remove the accumulated foreign condensibles.

Arranged within the chamber space 108 circumscribed by partition 98 is a conventional float valve 110 connected with a pipe 112 which is welded to bottom plate 46. Pipe 112 in turn connects with line 38 (FIG. 1) going back to the machine. The arrangement is such that overflow of liquid refrigerant across the upper edge 96 of wall 98 will establish a general liquid level 114 in chamber 108. As the chamber 108 liquid level rises appreciably above level 114 the float valve opens to discharge pure liquid refrigerant back to the machine. As the liquid level drops somewhat below level 114 the float valve closes. Thus, the float valve maintains a sufficient liquid level in chambar 108 to provide a desired pressure differential between space 68 and the liquid line 18, thus preventing the chamber 56 gas from bypassing the heat exchange coil through pressure equalizer opening 60, pipe 112, and line 38.

FEATURES OF THE INVENTION The illustrated purge unit incorporates two purge unit functions in a single shell, i.e. foreign non-condensibles purging and foreign condensibles purging. The single shell structure thus represents an improvement in compactness and parts simplicity, as well as a reduced number of external joints subject to leakage. It will also be noted that each of the various pipes 74, 94, 88, 92 and 112 are welded to a flat plate-like portion of the shell, not to a curved shell surface. The welds are therefore more likely to form good sealed joints with the shell walls.

An important feature of the invention is the removable or separable character of shell bottom wall 46, and the manner in which said bottom wall is used to mount the heat exchange coil 70. By removing bolts 48 it is possible to separate wall 46 from the upper portion of the shell to thus expose the shell interior for clean-out of sludge, residue or the like which may have accumulated during prolonged service. During the step of removing plate 46 coil 70 comes along with it, thus permitting inspection of the coil surface and possibly cleaning of the coil fins. Additionally the coil and its joints may be leak tested using any convenient acceptable method.

Partition 58 could perhaps be fixedly secured to shell 40 or top wall 42, but in that event the shell interior would not be completely exposed during the servicing operation, and clean out of the shell would not be so readily accomplished. Therefore it is preferred to make the partition 58- roof 62 assembly as a separable unit. Heat exchange coil 70 can of course be connected with an external source of cold water if it is desired to obtain continuous systemrunning and system-idle purging (without reliance on the machine refrigerant as a source of coolant). Plate 46 can be cup-shaped instead of flat, whereby to form part of the shell side wall.

It will be appreciated that some other structural modifications and rearrangements can be utilized while still practicing the invention as comprehended by the attached claims.

It is claimed:

1. In a refrigeration machine comprising a refrigerant condenser, a refrigerant evaporator, and a refrigerant compressor arranged in a closed cycle; and improved purge unit comprising an upstanding shell formed as upper and lower separable shell sections, an annular upstanding partition disposed within the shell to cooperate therewith in defining an upper outer annular chamber for collection of foreign non-condensibles, a first outer lower annular chamber for collection of foreign condensibles and liquid refrigerant; an annular upstanding weir within the second lower chamber for defining a float chamber therewithin, the weir being arranged so that pure liquid refrigerant can flow thereacross into the float chamber, and thence out of the purge unit; a heat exchange coil arranged in the upper annular chamber; means for passing coolant through the coil to cool gas flowing into the upper chamber; said first lower chamber being in unrestricted communication with the upper chamber whereby gaseous refrigerant and foreign condensibles liquify on the coil surfaces and are deposited in the first lower chamber by gravitational forces; foreign liquid removal means mounted on one of the shell sections for removing foreign condensibles accumulating in the first lower chamber; pure liquid refrigerant discharge means connected with the lower shell section in communication with the float chamber for discharging pure liquid refrigerant back to the machine; and means mounting the heat exchange coil on the lower shell section, whereby disassembly of the shell into its component sections exposes the shell interior for cleanout purposes; said heat exchange coil comprising inlet and outlet conduits extending upwardly from the shell lower section, a first helical conduit spiraling upwardly from the inlet conduit within the upper outer annular chamber, a return bend connected to the free end of the first helical conduit, a second helical conduit spiraling downwardly from the return bend to the outlet conduit, said helical conduits having their convolutions intertwined with one another.

2. In a refrigeration machine comprising a refrigerant condenser, a refrigerant evaporator, and a refrigerant compressor arranged in a closed cycle; an improved purge unit comprising an upstanding shell formed as upper and lower separable shell sections, said shell being internally partitioned to define an upper chamber for collection of foreign non-condensibles, a first lower chamber for collection of foreign condensibles and liquid refrigerant, and a second lower chamber for collection of pure liquid refrigerant; a heat exchange coil arranged in the upper chamber; means for passing coolant through the coil to cool gas flowing into the upper chamber; said first lower chamber being in unrestricted communication with the upper chamber whereby gaseous refrigerant and foreign condensibles liquify on the coil surfaces and are deposited in the first lower chamber by gravitational forces; foreign liquid removal means mounted on one of the shell sections for removing foreign condensibles accumulating in the first lower chamber; pure liquid refrigerant discharge means connected with the lower shell section in communication with the second lower chamber for discharging pure liquid refrigerant back to the machine; and means mounting the heat exchange coil on the lower shell section, whereby disassembly of the shell into its component sections exposes the shell interior for clean-out purposes; the pressure characteristics of the refrigerant providing condenser pressures above atmospheric pressure and evaporator pressures below atmospheric pressure, thus producing sufiicient pressure difierential for satisfactory purge operation without the use of a separate purge compressor; said purge shell having a sized gas inlet opening connected with the upper chamber, and a properly sized purge cooling coil within the upper chamber so that the purge cooling coil is maintained at the proper temperature to provide a satisfactory purge equilibrium pressure without discharging refrigerant vapor when no foreign elements are present in the shell, the purge shell having means responsive to shell pressure variations for detecting and discharging concentrations of foreign non-condensiblcs from the shell upper chamber when foreign non-condenribies are present.

References Cited UNITED STATES PATENTS 1,687,597 10/1928 Springer 62475 X 2,450,707 10/ 1948 Zwickl 62-85 2,577,598 12/1951 Zwickl 62-475 2,600,435 6/1952 Shapiro 62-303 X 3,145,544 8/1964 Weller 62475 X ROBERT A. OLEARY, Primary Examiner.

W. E. WAYNER, Assistant Examiner. 

